首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   175篇
  免费   2篇
  国内免费   9篇
安全科学   22篇
环保管理   24篇
综合类   38篇
基础理论   41篇
污染及防治   46篇
评价与监测   9篇
社会与环境   6篇
  2023年   1篇
  2022年   1篇
  2021年   2篇
  2020年   2篇
  2019年   3篇
  2018年   6篇
  2017年   6篇
  2016年   6篇
  2015年   2篇
  2014年   3篇
  2013年   18篇
  2012年   10篇
  2011年   9篇
  2010年   7篇
  2009年   6篇
  2008年   12篇
  2007年   16篇
  2006年   4篇
  2005年   8篇
  2004年   4篇
  2003年   7篇
  2002年   1篇
  2001年   3篇
  2000年   2篇
  1999年   2篇
  1998年   4篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1990年   2篇
  1988年   1篇
  1986年   2篇
  1984年   4篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1979年   2篇
  1977年   2篇
  1976年   3篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   3篇
  1958年   1篇
排序方式: 共有186条查询结果,搜索用时 31 毫秒
61.
2,2,4-trimethyl, 1,3-pentanediol monoisobutyrate (TPM) is a widely used solvent found in water-based coatings. Ambient measurements of TPM are reported here for the first time. Although this compound has been previously measured in indoor air, this study illustrates successful detection and quantification of TPM in ambient air at three locations in Southern California: Pico Rivera, Azusa, and Riverside. TPM was detected in every sample collected, with concentrations ranging from 0.7 to 49.5 parts per trillion (ppt). Collections took place during summer 2009, fall 2009, winter 2009/2010, and spring 2010, for 5–7 days during each season. The highest mean concentrations were observed during the summer months for each city, when coating activities are typically at their highest.

Implications 2,2,4-Trimethyl, 1,3-pentanediol monoisobutyrate (TPM) is a widely used solvent found in water-based coatings. Ambient measurements of TPM are reported here for the first time. The highest mean concentrations were observed during the summer months for each city, when coating activities are typically at their highest. Unreacted TPM constitutes approximately 0.01% of the total nonmethane hydrocarbon (NMHC) concentrations in the Los Angeles air basin and given its slow reactivity rate in forming ozone, this would be an approximate upper limit for the fraction of ozone that it is responsible for forming.  相似文献   
62.
At the European level, lacertid lizards have been proposed as potential model species for reptile ecotoxicology. We studied demographic and morphological aspects of natural field subpopulations of Podarcis bocagei inhabiting similar agricultural habitats which were either regularly exposed to pesticides, or not. Parameters examined in this study included population size and density, sex ratio, adult body size, fluctuating asymmetry in femoral pores and parasite prevalence. In general, we detected few statistically significant differences between the exposed and reference subpopulations. Although field situations are ecologically complex and factors other than pesticides may be acting, the absence of observable effects on field subpopulations is probably indicative that lizards are coping or compensating for this level of exposure.  相似文献   
63.
This study examined social capital development in three all-terrain vehicles (ATV) clubs in Maine using an adapted version of Lin’s (2001) social capital theory model. The structural components of social capital identified included collective assets and individual assets in the form of normative behavior and trust relationships. Also identified were counter-norms for individual ATV riders identified as having divergent norms from club members. The second component of social capital is access to and mobilization of network contacts and resources. Access networks in the context of the ATV clubs studied were identified as community and landowner relations while mobilization of resources was existent in club membership attempts toward self-governance and efforts of the statewide “umbrella” organization. Instrumental outcomes benefit society and expressive outcomes benefit the individual. Both types of returns are present in the data suggesting that ATV clubs are creating social capital. This is important information to clubs who desire to market themselves, improve their reputations, and enhance their volunteer association. It is of further interest to state governments who fund clubs through trail grants as proof that a return on investment is being realized. Theoretical and applied implications for these and other types of recreation-based volunteer associations (e.g., clubs, friends groups, advocacy groups) are presented.  相似文献   
64.
PROBLEM: As the number of older drivers grows, it is increasingly important to accurately identify at-risk drivers. This study tested clinical assessments predictive of real-time driving performance. METHOD: Selected assessment tools considered important in the identification of at-risk older drivers represented the domains of vision, cognition, motor performance, and driving knowledge. Participants were administered the battery of assessments followed by an on-road test. A univariate analysis was conducted to identify significant factors (<.05) to be included in a multivariate regression model. RESULTS: Assessments identified as independently associated with driving performance in the regression model included: FACTTM Contrast sensitivity slide-B, Rapid Pace Walk, UFOV rating, and MMSE total score. DISCUSSION: The domains of vision, cognitive, and motor performance were represented in the predictive model. SUMMARY: Due to the dynamic nature of the driving task, it is not likely that a single assessment tool will identify at risk drivers. IMPACT ON INDUSTRY: By standardizing the selection of clinical assessments used in driving evaluations, practitioners should be able to provide services more efficiently, more objectively, and more accurately to identify at-risk drivers.  相似文献   
65.
Polybrominated diphenyl ether in sewage sludge in Germany   总被引:2,自引:0,他引:2  
Knoth W  Mann W  Meyer R  Nebhuth J 《Chemosphere》2007,67(9):1831-1837
Sewage sludge samples from 11 municipal waste water treatment plants in Germany were collected from March 2002 to June 2003. Total Tri- to HpBDE concentrations (sum of significant congeners BDE 28, 47, 99, 153, 154 and 183) ranged from 12.5 to 288 (median 108) and DeBDE (BDE 209) concentrations from 97.1 to 2217 (median 256) ng/gd.m. BDE 209 dominated the congener profile. A significant change of the Tri- to HpBDE congener profile (% of total BDE 28, 47, 99, 153, 154, 183 without 209) in sludge from different stages of the waste water treatment process (primary sludge, secondary excess sludge and (dewatered) digested sludge), indicating a degradation of DeBDE to these congeners, was not observed.  相似文献   
66.
67.
The formation of winter ice, and its movement with the tides, has had a major influence on the life-history parameters of shallow-water populations of the rhizomatous marine angiosperm eelgrass (Zostera marina) in Nova Scotia, Canada. In this region, and annual form of eelgrass inhabits intertidal and shallow subtidal mudflats and a perennial form is common in subtidal areas. Where lowtide water depth was greater than winter ice thickness (25 cm), ice movement removed much of the aboveground biomass from perennial ramets, but did not influence the density of ramets. Measurements of primary production showed that perennial plants allocated a greater proportion of their total production to below-ground structures than measured in all previous studies on eelgrass. Thus perennials are well anchored in the sediment, are more able to withstand removal by ice, and have reserves available for production of new leaves when ice melts. In the spring, seed germination was greatest in areas where ice had removed whole plants (or their aboveground parts) than among mature ramets which had survived winter intact. Survival of seedlings (new genets) was not affected by shading from the adult canopy, but a shading experiment showed that competition for light with mature ramets had a significant negative effect on morphology, growth and the allocation of seedling biomass to below-ground parts, thus reducing the ability of new genets to survive ice disturbance in the next winter. The annual form ofZ. marina was restricted to areas where low tide water depth was much less than winter ice thickness. Annual plants did not survive winter, had small investment in below-ground parts and high reproductive effort, and overwintered as seeds. The genetic status of the two forms and the restriction of the annual to very shallow water are discussed in the light of previous work on eelgrass  相似文献   
68.
Concentrations of Na, K, Cl, Ca and Mg were measured in the spermatophoric plasma and certain other body fluids of Octopus dofleini martini. The most striking change associated with maturation and passage of the spermatophore in the male reproductive tract, was a decline in the concentration of NaCl in the spermatophoric plasma. This was completely reversed during the spermatophoric reaction owing to influx of salt from the seawater. The outer tunic of a spermatophore undergoing spermatophoric reaction is also permeable to other substances. It allows an influx of inorganic phosphate and glucose, and an efflux of organically bound nitrogen, carbohydrate and aminosugar.  相似文献   
69.
Changing lobster abundance and the destruction of kelp beds by sea urchins   总被引:1,自引:0,他引:1  
In a study area in Nova Scotia, Canada, abundance of the lobster Homarus americanus decreased by nearly 50% in 14 years. The lobster is a major predator of sea urchins, and during the past 6 years the sea urchin Strongylocentrotus droebachiensis has destroyed 70% of the beds of Laminaria spp. in the area. Implications for management are discussed.  相似文献   
70.
Monitoring is essential to track the long-term recovery of endangered species. Greater emphasis on habitat monitoring is especially important for taxa whose populations may be difficult to quantify (e.g., insects) or when true recovery (delisting) requires continuous species-specific habitat management. In this paper, we outline and implement a standardized framework to facilitate the integration of habitat monitoring with species recovery efforts. The framework has five parts: (1) identify appropriate sample units, (2) select measurable indicators of habitat requirements, (3) determine rating categories for these indicators, (4) design and implement appropriate data collection protocols, and (5) synthesize the ratings into an overall measure of habitat potential. Following these steps, we developed a set of recovery criteria to estimate habitat potential and initially assess restoration activities in the context of recovering an endangered insect, the Karner blue butterfly (Lycaeides melissa samuelis). We recommend basing the habitat potential grading scheme on recovery plan criteria, the latest information on species biology, and working hypotheses as needed. The habitat-based assessment framework helps to identify which recovery areas and habitat patches are worth investing in and what type of site-specific restoration work is needed. We propose that the transparency and decision-making process in endangered insect recovery efforts could be improved through adaptive management that explicitly identifies and tracks progress toward habitat objectives and ultimate population recovery.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号